Course Content

Introduction to SQL

1. Retrieving Data

Retrieving Individual Columns Retrieving Multiple Columns Retrieving All Columns Retrieving Distinct Rows Limiting Results Challenge: Find the Population of the Countries Challenge: Find All Countries Challenge: Find All Countries With Their IDs Challenge: Find Country Capitals Challenge: Find the Regions in Which All Countries Are Located

2. Sorting Retrieved Data

Sorting Data Challenge Sorting by Multiple Columns Challenge Specifying Sort Direction Challenge: Sort the Countries by Region and Capital Challenge: Sort Capitals in Descending Order Challenge: Sort Countries in Ascending Order Challenge: Find Countries, Their IDs, and Their Populations Challenge: Find Countries, IDs, Populations, Regions, and Sort Them Challenge: Find All Continents and Sort Them in Ascending Order

3. Filtering Data

Using the WHERE Clause Challenge The WHERE Clause Operators Challenge Checking for a Range of Values Checking for NO Value

4. Advanced Data Filtering

Using the AND Operator Challenge Using the OR operator Challenge Using the NOT Operator Challenge

5. Aggregate Functions

The AVG() Function Challenge The COUNT() Function Challenge The MAX() Function The MIN() Function Challenge The SUM() Function

Introduction to SQL

Sorting by Multiple Columns

We can also sort by multiple columns. We need to specify the column names separated by commas. Let’s look at the example that retrieves three columns and sorts the results by two of them: first by population and then by capital.

Task

Retrieve four columns using the SELECT statement, namely: continent, region, population, and capital (please retrieve these columns in this order). Then, sort the result by two of them: first by continent, then by population.

Here's a short example of the country table:

id	name	continent	region	surfacearea	capital	population
1	Japan	Asia	Eastern Asia	377829	Tokyo	126714000
2	Latvia	Europe	NULL	64589	Riga	2424200
3	Mexico	North America	Central America	1958201	Mexico City	98881000
...	...	...	...	...	...	...
15	Malta	Europe	Southern Europe	316	Valletta	380200

Everything was clear?

Section 2. Chapter 3